Take boiled and peeled potatoes in a bowl and roughly mash them(don’t make a paste )
Heat oil (or use half ghee and half oil if you wish) in a pan.
Add the tempering ingredients ,when seeds start crackling ,add slit green chilies and saute for a few seconds.
Remove the pan from the flame and add all the powdered spices(turmeric,chili powder,coriander powder)
Immediately add beaten yogurt and stir once.(see the tips)
Put the pan on the gas and add boiled potatoes and ginger and mix.
Add water (depends on how thick curry you prefer)
Now add salt and let it boil on medium flame .Keep stirring till it start boiling to avoid curdling.
Cook for approx 3-4 minutes on medium flame.
When it starts to thicken then add chopped fresh coriander and switch off the flame
Serve hot with poori, paratha or any bread of your choice.